The present invention relates to a process and to an installation for the separation of air by cryogenic distillation.
It is known to produce an air gas under pressure by vaporizing a pressurized liquid in an exchange line of an air separation unit by heat exchange with a compressed gas at a cryogenic temperature. Units of this type are known from FR-A-2 688 052, EP-A-0 644 388, EP-A-1 014 020 and patent application FR 03/01722.
The energy efficiency of the known devices is not excellent, as it is necessary to exhaust the heat influx associated with the cryogenic compression.
In addition, in the case of the diagrams such as that illustrated in FIG. 7 of U.S. Pat. No. 5,475,980, the entire turbine coupled to the cold booster is associated with an energy dissipation system (oil brake) incorporated onto the shaft of the machines and technologically limited to low power levels (of around 70 kW).
However, this type of process appears to be economically advantageous, in particular when the energy is of low value or available at low cost. It is therefore potentially advantageous to be able to exceed the technological limit of the oil brake incorporated on the shaft of the turbine/booster assembly.